Apparatus for screening pulp and the like



May 8, 1928. 1,669,029

, R. E. WAGNER APPARATUS FOR SCREENING PULP AND THE LIKE Filed Aug. 16, 1927 2 Sheets-Sheet 1 May 8, 1928.

R. E. WAGNER APPARATUS FOR SCREENING PULP AND'THE LIKE 2 Sheets-Sheet 2 Filed Aug. 16, 1,927

Inven/or:

Patented May 8, 1928.

I s r ALT ES1 RUDOLF ERNST WAGNER, 0E KARLSTAD, SWEDEN.

APPARATUS FOR SCREENING PULP AND THE LIKE.

Application filed August 16f1927/Se'ri'a1 No. 213,307, and "in Sweden .Tune'22, 1925.

The present invention relates to an apparatus for screeningmechanical pulp, cellulose or'other body suspended in a liquid, said apparatus being provided with a stationary or rotary perforatedscreen, and with adrum, wheel, or the like PIOVlClQCl' pulp, whiclris diluted witlrwater, against the perforations in the screen 1n order that the fine fibres shall pass througlr the'screen,

whereas the'coarse fibres shall stop on the inner surface of the screen'and afterwards be I n t v v p ever, to provide the apparatus with a re causedto leave the'apparatus atone of"its ends. Experience'hasproved, however, that the wings orblades on the -drum tend'to' throw the pulp througlr the screen wlth' too" great a force, particularly at those points where i the pulp or diluting liquid "is introduced, with the result that theperforations in the screenbecomecloggedby coarse fibres very rapidly.

The present invention has for it'spurpose to avoid this'disadvantageand to effect such admission of. pulp and of" dilutingliq'uid' q p I H apparatus 111' cross sectlon, the left hai'id" that the pulp and 'the diluting liquid will be caused to perform pulsations in a direction"perpendicular to the screen; surface,

which action has provedto be exceedinglyv contributive to obtaining a soft and smooth screening actlon and to avoiding clogging of the perforations; For this purpose the apparatus according to the invention is broadly characterized inthat'thescreen is provided with two or more belts or zones in which the screen is wholeunperforated or the perforations in'thescreen are covered, and in the spaces within which zones are found inlets forpulp orfor diluting liquid open, said zones bein 'separated by perforat ed zones or sections of the screeng The pulp and the' diluting liquid will thus be admitted into zones of the space between the screen and the drum in which zon'esthescreen is unperforated, and'the pulp and the diluting liquid can thereforenot be thrown directly out tlirough the screen by the 'wings'or blades surface, andinto the perforated sections intermediate the unperforated zones. Practical tcsts' have proved that s in this manner pulsations 'arecaused in the liquid perpendicular to the screen surfaceiwhich give a soft andfsmoothscreening action and which obviously prevent the coarse pulp .from

sticking to the screen surface and clogging the perforations in the same."

It is usual to make such screening appa,

ratus with a cylindrical *horizontal screen,

and" it will be"-obvious thatin this case as welliasinother cases the pulp and the dilu-tingliquid may be introduced intothe above mentioned zones in a direction from" the -outsideinwards.- It is "preferred, h0wcei-ving ch'ainberfor the pulp at one end ,of the drum, from whichchamberopennr for passages'lead 111 the drum andopen at the" circumference of the drum at points inside half on-the line I-f-I' in Fig. 1, and the righthai'id' hal'fbn tli 'lihII-II in Fig) 1.

The a parat s illustrated comprises a bottonr framel provided with feet '2 and an outlet 3'for' tlie fine' fibres, the accepted Secured to said" frame 1' are two stock. side frames or end pla tes 4 and '5 which are connected at the top by means of a U-shaped longitudinal brace G. Secured to the front end plzitetis an inlet? for-the pulp to be screened, aiidjournalled ina bearing 8 mounted on said inlet 7 and'in'a bearing 9 inollintec'l on the'rear cndplate 5 'is'ashaft lOfpi'ovided with a pulley 11. Said shaft 10 carriesthe'druin or wheel which, as a unit, isre'fel enccd 12, and which, in the in stance illustrated, coniprise's hubs or centers 13*and1-(L mounted on tlie'shaft 10 andan intermediate ring 15, between which three members 13,15, 14 tliere'are providedrings or cylinders 1(5'and 17 of sheetfmetal or the like -whicli together with the first-named menibers form' a cylindrical surface on the" drum 12. The hub 13 is located at a distance from the end plate 4 and inlet 7 so that a receiving chamber 18 for the pulp is formed between said members. From said chamber apertures 19 in the outer flange on the hub 13 lead to the space outside the drum 12. Leading from said chamber 18 are also axially disposed tubes 20 to passages 21 in the ring 15, which passages open at the outer circumference of the drum, as well as axially disposed tubes 22 leading to passages 23 in the hub 14, which passages also open at the outer circumference of the drum. Secured to the hub 13 in the receiving chamber 18 are radially directed Wings which, upon rotation of the drum, catch the admitted pulp and put it into a rotary motion. Mounted on the outer circumference of the drum 12 are blades or wings 25, preferably made of L-shaped bars, which are placed slightly obliquely to the aXial direction in such manner that upon rotation of the drum they cause the pulp to move in the axial direction from the inlet end. Said wings extend along the entire length of the apparatus and are supported at its rear end by a ring 26. Between the wings 25 shorter wings 27 are mounted which only extend from the hub 14 to. the rear end of the apparatus where they also are secured to the ring 26. Said shorter wings 27 are preferably also obliquely placed and made of L-shaped bars.

Tubes 28 extend through the rear end plate 5 into the apparatus inside the ring 26 andthe wings 25 and 27. Said tubes 28 are provided with discharge openings 29 for diluting liquid.

Mounted between the two end plates 4 and 5 is the screen 30 of the apparatus, said screen being stationary in the instance illustrated, but it will be understood that it may also be made rotary. Said screen surrounds the rotary drum 12. As shown in Fig. 1, said screen is provided with belts or Zones 31 radially outside the orifices of the pas sages 21 and 23 and radially. outside the discharge openings 29 in the tubes 28, in which belts or zones 31 the screen is whole, i. e. is not provided with perforations. The screen is preferably reinforced by means of rings 32 of angle iron or the like placed around said belts or Zones 31. i

In order to render it possible to Wash the outer surface of the screen and thus to keep the perforations in the screen free from resin and the like, there are provided sprinkling tubes outside the screen, and in the embodiment illustrated in which the screen is stationary, said tubes are adapted to rotate around the screen in order to make it possible to sprinkle the entire surface of the screen. For this purpose the sprinkling tubes 33 are secured to two rings 34 and 35 which are journalled on the end plates 4 and 5 by means of interleaving seals, and for this purpose each ring is made in two halves connected by means of screw bolts 36, Fig. 2. The two rings 34 and 35 are joined to each other, besides by means of the sprinkling tubes 33, also by means of longitudinal bracing rods 37 or the like, so that said two rings form together with said rods and tubes an assembled unit rotatable around the screen. The rear ring 35 is provided with a row of teeth 38 engaged by a toothed pinion 39 mounted on a shaft 40, which is journalled in a bearing 41 on the rear end plate 5 and on which a chain sprocket wheel 42 is mounted, which is connected by means of a chain 43 to a chain sprocket wheel 44 on the shaft 10. ll-"hen the drum 12 rotates, the rings 34 and 35 and the sprinkling tubes 33 will thus also be rotated around the screen 30, but at a less speed. Passages 45 are provided in. the ring 34 which communicate with the sprinkling tubes 33 and also with an annular groove or channel 46 in the end plate 4, which channel is surrounded by the ring 34 and to which leads an axial passage 47 extending from the. outside of the end plate 4, to which passage 47 a water pipe is supposed to be connected at the valve 48. 49 denotes a valve provided in the inlet 7 for the purpose of admitting water into the receiving chamber 18 for flushing the interior of the apparatus, when required. 50 denotes a pipe for admitting water at the rear end of the apparatus into the coarse pulp or tailings collecting at said end during operation of the apparatus, before such pulp reaches the outlet 51,Fig. 2, formed in the rear end plate 5.

On the-outside of the drum 12 adjacent to the apertures 19 and the orifices of the passages 21 there are provided adjustable plates 52 which may be secured to the drum, for instance, by means of bolts passing through oblong slots in said plates. These plates serve to adjust the area of said apertures and orifices.

The pulp to be screened is admitted into the apparatus through the inlet 7 and arrives into the receiving chamber 18 where it is caught by the wings 24 and is thus put in retation and flows in a radial direction through the apertures 19 out into the space between the drum and the screen. The pulp will then first meet the cylindrical surface,

53 of an inwardly extending flange on the end plate 4, and is thus forced to assume an axial direction of flow towards the rear end of the apparatus, but will, of course, still continue its rotary motion. It has been found that in this way and owing to the influence exerted by the rotary wings 25 on the layer of pulp inside the screen, a pulsating motion is set up in the pulp perpendicularly to the screen, so that the screening is effected smoothly and evenly and clogging of the perforations is preventecll Owingzzto the screening the pulpinside the screen will ofcoursegradually assume/a coarsercon sistency, but when during. its axial motion it arrives into the first unperforatedzone 31 of the screen, it meets fresh pulp flowing z sating action in the next perforated portion or section of the screen. At the next unperforated zone 31 fresh pulp flows out from the passages 23, and when the screening of said pulp has been effected in a similar manner, the remaining pulp is mixed with other suitable diluting liquid, for instance water, which flows out radially from the discharge apertures 29 on the tube 28 against a third unperforated zone 31 of the screen. In this manner a complete screening of the pulp is effected by a continuous pulsating action, so that practically only coarse pulp'remains when the pulp reaches the rear end of the apparatus. During this last period of the screening water from the tubes 28 is con stantly added to the coarse pulp so that all good fibres are separated as far as possible from the failings and flow out through the screen, to be discharged, together with the accepted stock, through the outlet 3. In order to facilitate the discharge, the tailings may be diluted with water admitted through the pipe 50 before the tailings reach the outlet 51. By means of the adjustable plates 52 the two first groups of inlet openings for the pulp are regulated in such manner that a suitable dilution of the remaining pulp will be obtained by the admission of fresh pulp through the following group of inlet openings.

As above mentioned, itis by no means necessary to introduce the pulp in a direction from the inside of the drum radially outwards, but the pulp may also be introduced within the screen in a direction from the outside inwards, and also in other respects the invention is not limited to the embodiment above described and illustrated in the drawing, since it will be understood that the details of said embodiment may be modified in several ways within the scope of the invention.

I claim 1. In an apparatus of the character described, the combination of a perforated screen, a drum rotatable within said screen and provided with wings, said screen and said drum forming a space for receiving pulp, said screen being provided with a number of zones in which the screen is unscreen, a. drum rotatable within} said screen and provided with wings, said screen and said drum forming a space for receiving pulp, said screen being provided with a number of zones in which the screen is unperforated and which are separated by per.- forated portions of the screen, a receiving chamber for pulp at one end of said drum, and passages leading from said chamber and opening at the circumference of said drum at points inside said unperforated zones of said screen;

In an apparatus of the character described the combination of a perforated screen, a drum rotatable within said screen and provided with wings, said screen and said drum forming a space for receiving pulp, said screen being provided with a number of zones in'which the screen is unperforated and which are separated by perforated portions of the screen, a receiving chamber for pulp at one end of said drum, passage-s leading from said chamber and opening at the circun'lference of said drum at points inside said unperforated zones of said screen, and adjustable plates adjacent to the openings of said passages at the circumference of said drum.

4. In an apparatus of the character described, the combination of a stationary perforated screen, a drum rotatable within said screen and provided with wings, said screen and said drum forming a space for receiving pulp, said screen being provided with a number of zones in which the screen is unperforated and which are separated by perforated portions of the screen, inlets for the pulp opening into said space inside said unperforated zones, and sprinkling tubes rotatable around said screen.

5. In an apparatus of the character de; scribed, the combination of a perforated screen, a drum rotatable within said screen and provided with wings, said screen and said drum forming a space for receiving pulp, said screen being provided with a number of zones in which the screen is un perforated and which are separated by perforated portions of the screen, a receiving chamber for. pulp at one end of said drum, passages leading from said chamber and opening at the circumference of said drum at points inside'said unperforated zones of said screen, and sprinkling tubes rotatable around said screen.

6. In an apparatus of the character described, the combination of a perforated screen, a drum rotatable within said screen and provided with wings, said screen and loo said drum forming a space for receiving pulp, said screen being provided with a number of zones in which the screen is unperforated and which are separated by perforated portions of the screen, a receiving chamber for pulp at one end of said drum, passages leading from said chamber and opening at the circumference of said drum at points inside said unperforated zones of said screen, an outlet for coarse pulp at the 10 end of the apparatus remote from said re ceiving chamber, and a Water inlet pipe at said end of the apparatus.

RUDOLF ERNST XVAGHER. 

